CA2194522A1 - Variable ratio drive pulley - Google Patents
Variable ratio drive pulleyInfo
- Publication number
- CA2194522A1 CA2194522A1 CA002194522A CA2194522A CA2194522A1 CA 2194522 A1 CA2194522 A1 CA 2194522A1 CA 002194522 A CA002194522 A CA 002194522A CA 2194522 A CA2194522 A CA 2194522A CA 2194522 A1 CA2194522 A1 CA 2194522A1
- Authority
- CA
- Canada
- Prior art keywords
- shaft
- flange
- movable flange
- drive pulley
- variable ratio
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
- F16H55/32—Friction members
- F16H55/52—Pulleys or friction discs of adjustable construction
- F16H55/56—Pulleys or friction discs of adjustable construction of which the bearing parts are relatively axially adjustable
- F16H55/563—Pulleys or friction discs of adjustable construction of which the bearing parts are relatively axially adjustable actuated by centrifugal masses
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- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Pulleys (AREA)
Abstract
A variable ratio drive pulley of the type employed in snowmobiles to transmit a drive from the snowmobile engine to a variable ratio belt drive transmission has a fixed flange and an opposed movable flange which cooperate to drive the belt. The drive pulley is coupled to rotate with the engine crankshaft and the movable flange incorporates a centrifugal means that operates to advance it towards the fixed flange, with a force that increases with speed of rotation, to grip the transmission belt between the flanges and apply a driving torque thereto, this torque being applied by both the flanges. To reduce the effects of engine induced vibrations on the centrifugal means and on the movable flange, a damping structure is incorporated in the torque path between the engine crankshaft and the centrifugal means and movable flange. The damping structure comprises a hexagonal rubber ring that is positioned between a driving head and the hub of the drive pulley to absorb vibrations which would otherwise be transmitted between these.
Description
BACKGROUND OF THE INVENTION
(a) Field of the Invention This invention relates to a new or improved variable ratio drive pulley or clutch for the transmission of a driving torque to a flexible belt in a belt drive arrangement, the new pulley being particularly although not exclusively useful in a snowmobile drive transmission.
(b) Description of the Prior Art In my U.S. Patent No. 5,326,330, the disclosure of which is hereby incorporated by reference, I describe a drive pulley as utilized in a snowmobile transmission. The drive pulley includes a central axial shaft carrying two frusto-conical flanges one of which is fixed to rotate with the shaft and the other of which is guided to move axially towards and away from the fixed flange. The movable flange is urged away from the fixed flange by a spring, and the pulley includes an arrangement of pivoted weighted levers designed on rotation of the pulley to generate an axial force on the movable flange to displace it towards the fixed flange, this force increasing with rotational speed of the pulley.
A drive pulley of the type discussed above, otherwise described as a clutch, is generally coupled directly to the crankshaft of the engine and thus is subjected to engine induced vibrations at both pulley flanges. In particular, the drive pulley of a snowmobile transmission is commonly mounted directly to the crankshaft of a high specific horsepower two-stroke engine and may be subjected to a very high level of vibration, both bending and torslonal, emanatlng from the englne crankshaft. Thls can be deleterlous both to the force generatlng means and to the drlve belt ltself. Indeed lt ls common for drlve pulleys of thls klnd used ln snowmoblles to experlence wear ln the load mechanlsm or force generatlng means.
Thls wear ls caused malnly by torslonal vlbratlon, and to malntaln optlmum performance of the system lt may be necessary to replace varlous components of the mechanlsm perlodlcally.
The constantly lncreaslng power outputs of snowmoblle englnes applles addltlonal loadlng stresses to the components so that there ls a need to lmprove the reslstance of drlve pulleys to englne lnduced vlbratlons.
SUMMARY OF THE INVENTION
The lnventlon accordlngly provldes a varlable ratlo drlve pulley comprlslng: a) a shaft; b) confrontlng fixed and movable frusto-conlcal flanges mounted on sald shaft to rotate therewlth, sald flxed flange belng flxed to sald shaft and sald movable flange belng gulded to move axlally of sald shaft towards and away from sald flxed flange; c) a sprlng ln sald pulley belng operatlve to urge sald movable flange away from sald flxed flange; d) a centrlfugally responslve mechanlsm ln sald pulley belng operatlve on rotatlon of sald pulley to generate a force urglng sald movable flange towards sald flxed flange, such force lncreaslng wlth the rotatlonal speed of sald pulley; e) a torque transmltter for transmlttlng a drivlng torque from sald shaft to sald movable flange, sald torque transmltter comprlslng an operatlng head assembly flxed to rotate wlth sald shaft, sald head assembly lncludlng a plurallty of radlal drlvlng arms equlangularly spaced about the axls of sald shaft, sald drlvlng arms engaglng abutment surfaces on sald movable flange at a radlal spaclng from sald shaft axis to dellver drlvlng torque to sald movable flange; f) sald head assembly and sald movable flange havlng cooperatlng axlally extendlng gulde surfaces by whlch sald movable flange ls gulded from movement axlally of sald shaft; g) sald head assembly belng connected to sald shaft through a damplng element sald damplng element belng operatlve to attenuate transmlsslon of torslonal vlbratlons from sald shaft to sald movable flange.
The movable flange ls preferably gulded for axlal movement on an axlally extendlng hollow lnput shaft or sleeve, the flxed flange belng attached to the sleeve, and the sleeve carrylng a hub through whlch torque ls transmltted to the centrlfugally responslve means by way of the damplng element. In thls way, the effects of englne-lnduced vlbratlons are absorbed and dampened, and thls protects the centrlfugally responslve means from the damaglng effects of such vlbratlons. Furthermore the effects of vlbratlons transmltted to the drlve belt from the movable flange are substantially ellmlnated.
The element can be posltloned at any convenlent locatlon ln the operatlng head assembly, and ln one preferred arrangement ls located ln the hub reglon thereof.
An added beneflt of the lncorporatlon of the damplng element ls that lt effects a slgnlflcant reductlon ln the level of nolse generated by the varlable ratlo drlve pulley ln operatlon. Thus the lnventlon also provldes a method for reduclng the nolse output of varlable ratlo pulleys of thls general type.
BRIEF DESCRIPTION OF THE DRAWINGS:
The lnventlon wlll further be descrlbed, by way of example only, wlth reference to the accompanylng drawlngs whereln:
Flgure 1 ls a partlally fragmentary cross-sectlonal vlew of a preferred embodlment of varlable ratlo drlve pulley ln accordance wlth the lnventlon;
Flgure 2 ls a sectlonal vlew taken generally on the llne II-II ln Flgure l;
Flgure 3 ls an exploded sectlonal vlew of certaln components shown ln Flgure 2; and Flgure 4 ls a vlew correspondlng to Flgure 2 but showlng a modlfled embodlment of varlable ratlo drlve pulley ln accordance wlth the lnventlon.
DESCRIPTION OF THE PR~h~K~ EMBODIMENT
Referrlng to Flgure 2, the drlve pulley comprlses a hollow tubular shaft 11 whlch carrles opposed frusto-conlcal flanges 12 and 13. The flange 12 ls a flxed flange that ls rlgldly secured to the shaft 11, whereas the flange 13 ls a movable flange gulded for movement axlally of the shaft 11 towards and away from the flxed flange by a bushlng 14. The rear slde of the movable flange 13 carrles ln a hollow houslng 15 closed on lts rear slde by a convex cover 16 that ls detachably secured to the houslng by capscrews 17, the cover havlng a central axlally pro~ectlng hub 18 that carrles a tubular bushlng 19 whlch slldably engages a reduced dlameter portlon 20 of the shaft 11.
The capscrews 17 are slx ln number and are recelved ln threaded engagement ln bores of axlally extendlng bosses 23 (Flgure 2) arranged ln palrs, each boss belng assoclated wlth an ax~ally extendlng gulde wall 24 whlch walls are lntegral wlth the rear slde of the movable flange 13. The gulde walls cooperate wlth the llmbs 25 of a three-armed operatlng head 26 whlch ls mounted to rotate wlth the shaft 11. The operatlng head 26 transmlts drlvlng torque from the shaft 11 to the movable flange whlle permlttlng the latter to move axlally wlth respect to the shaft 11. More speclflcally, near lts extremlty each of the llmbs 25 carrles a palr of pads 27 of low-frlctlon materlal each seated ln a counterbore ln one slde of the llmb, each pad 27 belng ln slldlng engagement wlth one of the gulde walls 24, sprlng means (not shown) belng provlded to take up any clearance between the llmbs 25, pads 27 and gulde walls 24.
Each llmb 25 also carrles a roller 30 rotatably mounted on an axls that ls tangentlal to and ln a plane perpendlcular to the axls of the shaft 11, and ls coaxlal wlth the slldlng pads 27. Each roller 30 ls posltloned between blfurcate flngers 28 belng carrled on a pln 29 mounted ln bores ln the flngers 28 and allgned wlth the pads 27.
Each roller 30 ls mounted to cooperate wlth a cam surface 31 of an ad~ustlng lever 32 whlch extends generally radlally wlth respect to the axls of the shaft 11 and ls plvotally mounted on the rear slde of the movable flange 13 on an axls generally parallel to that of the roller 30. As ls more fully descrlbed ln my U.S. Patent 5,326,330, the plvotal mountlng of each ad~ustlng lever lncludes an ad~ustable 2~ 94522 eccentric 33 by means of whlch the location of the plvotal axis of the lever 32 can be ad~usted. The operation of this ad~ustment in varylng the performance characterlstlcs of the pulley ls as described ln my above ldentlfled prevlous patent, and ls not further descrlbed herein.
As prevlously mentloned, the three-armed operatlng head 26 ls flxed to rotate with the shaft 11. However it is structured so that lt lncludes a vlbratlon absorblng structure thereby to attenuate or ellmlnate vlbratlons transmltted from the shaft to the movable pulley flange 13. Referrlng to Flgure 3, the operatlng head 26 has a large hollow central hub 35 whlch has an lnterlor surface 36 of tapered hexagonal proflle. The proflle reaches a mlnlmum slze at a locatlon 37 near the rlght hand end of the hub as seen ln Flgure 3, and then flares outwardly. Each facet of the lnternal surface 36 has machlned thereln a part-cyllndrical recess 38, the recesses 38 being coaxlal wlth respect to the central axls 40 and each termlnatlng ln a shoulder 41, the shoulders lylng ln a common plane at rlght angles to the axls 40.
A vlbratlon absorbent reslllent damplng member 45 ls slzed to be posltloned wlthln the hub 35 near one end (the rlght hand end as seen ln Figure 3) of the lnterlor surface 36. The damplng member 45 ls of a sultable reslllent materlal such as polypropylene, natural and synthetlc rubbers and the llke, and ls ln the form of an hexagonal rlng slzed to flt closely agalnst the lnternal surface 36. Thus, the outslde of the member 45 has a flrst tapered hexagonal surface 46 and a second shorter expanding hexagonal surface 47, the lnner surface 48 belng contlnuously tapered from one end to the other, and the end surfaces belng ln planes perpendlcular to the axls 40. The slightly enlarged sectlon 47 of the damplng member 45 acts to retaln the latter agalnst dlsplacement rearwardly (to the left as seen ln Flgure 2) and separatlon from the operatlng head 26.
A tubular drlver hub 50 secures the operatlng head 26 wlth respect to the shaft 11, and ls most clearly shown ln Flgure 3. The drlver hub 50 has a screwthreaded bore 51 wlth short cyllndrlcal counterbores at opposlte ends thereof, and has at a medlal posltlon ln lts length a pro~ectlng external annular flange 52. As seen ln Flgure 3, to the rlght of the flange 52 there ls a tapered hexagonal surface sectlon 53 whlch has a proflle that corresponds to that of the lnner surface 48 of the damplng member. Stlll wlth reference to Flgure 3, to the left of the flange 52 the drlver hub has a short cyllndrlcal sectlon 54, and termlnates l~n a short hexagonal drlvlng sectlon 55. The outer dlameter of the flange 52 ls of a slze to flt wlthln the cyllndrlcally formed recesses 38.
In the assembled condltlon, the damplng member 50 ls fltted wlthln the hub 35 and ls posltloned ad~acent a flat annular washer 56 whlch ln turn ls supported agalnst an annular shoulder 57 on the shaft 11 (Flgure 2). The drlver hub 50 ls ln engagement wlth screwthreaded sectlon 58 of the shaft 11, wlth the flange 52 recelved ln the recesses 38 so that the damplng member 45 ls contalned at lts opposlte ends between the flange 52 and the washer 56 and ls contalned at lts lnternal and external perlpherles by the tapered hexagonal drlver surface 53 and the tapered hexagonal hub surface 36 respectlvely. Durlng 2 1 ~4522 assembly, after the flxed flange 12 has been lnstalled on the shaft, the movable flange 13 ls then mounted and the washer 56 placed agalnst the shoulder 57 of the shaft. The damplng member 45 ls then fltted wlthln the bore of the operatlng head 26, and these are then passed over the shaft to the posltlon shown ln Flgure 2 where the damplng member 45 abuts the washer 56. The drlver hub 50 ls then lnstalled, belng threaded onto the screwthreaded sectlon 58 of the shaft to brlng the flange 52 lnto abutment wlth the end surface of the damplng member 45, and compress the latter to the degree deslred.
In the fully lnstalled posltlon the washer 56 ls engaged and clamped agalnst the shoulder 57 by the forward end of the drlver hub 50. Rotatlon of the drlver hub 50 can be effected by a wrench or the llke engaglng the hexagonal drlve sectlon 55 of the hub. In the fully lnstalled posltlon therefore the damplng member 45 ls contalned at lts ends between the washer 56 and the hub flange 52, and on lts lnner and outer sldes between the hexagonal hub surface 53 and the hexagonal surface sectlons 36, 37 of the drlver 26 respectlvely. In thls condltlon there ls no metal-to-metal contact between the operatlng head 26 and the parts (hub 50 and washer 56) attached to the shaft 11. Thus there ls substantlal clearance between the flange 52 and the recesses 38 and shoulders 41 of the operatlng head and between the outer perlphery of the washer 56 and the hub 35 of the operatlng head that no metal-to-metal contact can occur, even lf the hub 50 and the washer 56 undergo substantlal torslonal and bendlng vlbratlon transmltted from the shaft 11.
~ 1 94522 From the foregolng descrlptlon and from a conslderatlon of Flgure 2 of the drawlngs lt wlll be appreclated that the components descrlbed effectlvely flx the operatlng head 26 with respect to the shaft 11 so that torque from the shaft can be transmltted to the operatlng head 26 and thence to the welghted pivoted levers 32 and the movable pulley flange 13.
However as noted above, there ls no contlnuous metal-to-metal engagement ln the path between the shaft 11 and the operatlng head 26. Instead, torque from the shaft ls transmltted through the drlver hub 50 to the damping member 45 and from the latter to the operatlng head 26. Rellable torque transmlsslon ls ensured by the hexagonal shape of the damplng member 45, there belng no need for the latter to be bonded elther to the drlver hub 50 or to the operatlng head 26.
A colled compresslon sprlng 60 ls posltloned wlth one end seated agalnst the cover 16 around the hub 18, and lts opposlte end seated agalnst the flange 52 around the cyllndrlcal sectlon 54 of the drlver hub 50. As lndlcated prevlously, the cover 16 ls flxedly secured to the movable flange 13 by capscrews 17, thls conflguratlon allows the sprlng 60 to apply a compresslve load to and press the lnner sectlon of the movable flange 13 agalnst the washer 56 (adoptlng the posltlon shown ln Flgure 2). When the parts are posltloned as shown ln Flgure 2 wlth the movable flange 13 at lts maxlmum spaclng from the flxed flange 12, the compresslve loadlng applled to the sprlng 60 ls mlnlmal. A low-frlctlon plastlc carrler may be lnterposed between the hub 18 and the ad~acent end of the sprlng 60 to avold frettlng or abraslve wear of hub 18 due to vlbratlon of 2 ~ 94522 the sprlng.
In general, the operatlng characterlstlcs of the drlve pulley are slmllar to those of the drlve pulley descrlbed ln my U.S. Patent 5,326,330. When the shaft 11 ls statlonary or rotatlng at low speed, the components occupy the posltlons shown ln Flgure 2 wlth the movable flange 13 at maxlmum spaclng from the flxed flange 12 so that the flanges do not apply any drlvlng torque to the V-shaped drlvlng belt (not shown) whlch ls located therebetween. Wlth lncreaslng speeds of rotatlon, the centrlfugal force actlng on the ad~ustable levers 32 tends to plvot these outwardly around thelr plvotal mountlngs so that the cam surfaces 31 lnteract wlth the rollers 32 to develop an axlal thrust urglng the movable flange towards the fixed flange. When thls axlal thrust reaches a sufflclent level, lt overcomes the loadlng of the sprlng 60 and the flange 13 is dlsplaced towards the flxed flange 12 to engage the drlve belt therebetween, as ls well understood.
The damplng arrangement descrlbed acts to lsolate the movable flange and all the components assoclated therewlth lncludlng the bushlng 14, the centrlfugal levers 32 and thelr eccentrlcs 33, the cover 16, gulde walls 24 and the operatlng head 26 from the effects of torslonal vlbratlons generated on the englne crankshaft (not shown) to whlch the shaft 11 ls connected. These vlbratlons are partlcularly troublesome ln hlgh output two-stroke englnes of the type commonly used ln recreatlonal vehlcles such as snowmoblles. The damplng assembly lmproves the performance and rellablllty of such products whlle enabllng them to operate more quletly.
2 ~ 94522 Furthermore, testlng has shown that the servlce llfe of a snowmoblle drlve pulley of the type dlsclosed ln my U.S.
Patent 5,326,320 can be greatly lmproved by the addltlon of a damplng arrangement as descrlbed above. In some tests lt was found that the servlce llfe of the drlve pulley was lncreased by a factor of up to 10 before malntenance was requlred.
The use of a damplng arrangement as descrlbed offers a further ma~or beneflt ln that lt provldes a method of achlevlng a slgnlflcant reductlon ln nolse generated durlng operatlon of the drlve pulley. Varlous elements of the mechanlsm lnvolve metal-to-metal or metal-to-plastlc contact and there wlll usually be sufflclent clearance between the components that when the pulley ls sub~ected to vlbratlons, rattllng and hammerlng nolses can be generated. Such nolses are greatly reduced by lncorporatlng a damplng arrangement as descrlbed slnce the latter ls effectlve to more or less completely attenuate vlbratlons whlch otherwlse would be transmltted through the movable components.
Referrlng now to Flgure 4 the overall conflguratlon of the varlable ratlo drlve pulley lllustrated thereln ls slmllar to that as shown ln Flgures 1 to 3 and llke reference numbers are used to ldentlfy llke elements thereof. In contrast to the flrst descrlbed embodlment, ln Flgure 4 there ls no damplng member 45 located ln the reglon of the hub, but rather the three-armed operatlng head 26a has an lntegral hub 35a and lncludes modlfled arms 25a carrylng the damplng elements. More speclflcally, ln each arm there ls a damplng element 45a ln the form of a flat rectangular plece of reslllent damplng materlal bonded to a surface of the arm 25a, these damplng elements 45a lying ln a common plane that ls at rlght angles to the axls of the shaft 11. On lts opposlte slde, each damplng element 45a ls bonded to a co-extenslve flat wall 64 of a carrler 65, thls carrler havlng lntegrally formed thereon the flngers 28 that support the pln 29 and roller 30. As before, the materlal of the damplng elements can be of any sultable natural or synthetlc rubber, for example NBR (Nltrlle-butadlene) of a hardness of 65+5 Shore A.
It wlll be seen that as wlth the flrst descrlbed embodlment, ln the embodlment of Flgure 4 the centrlfugally mechanlsm lnvolvlng the lnter-engaglng rollers 30 and levers 32 as well as the movable flange 13 ltself are effectlvely lsolated from vlbratlons. Thls embodlment also ls effectlve to slgnlflcantly reduce the generatlon of nolse.
Although the lnventlon has been exempllfled ln the foregolng by the descrlptlon of presently preferred embodlments of varlable ratlo drlve pulley, and methods of reduclng the vlbratlon and nolse output thereof, lt wlll be understood that many modlflcatlons can be made ln the detalls of the lnventlon.
Thus, the lnternal and external surfaces of the damplng member 45 ln Flgures 1 to 3 are descrlbed as belng hexagonal, whlle lt wlll be evldent that many other polygonal and non-clrcular shapes would be feaslble. Indeed by bondlng the damplng member 45 (Flgure 2) to the drlver hub 50 andtor to the operatlng head hub 35, lt would be posslble to utlllze cyllndrlcal or conlcal shapes for such bonded surfaces. Slmllarly the damplng member although lllustrated ln Flgures 1 to 3 as belng lncorporated 21 94~22 between the operatlng head and the drlver hub, could ln fact be lncorporated wlthln the operatlng head itself e.g. as shown ln Flgure 4, the determlnlng requlrement belng that the movable flange 13, the welghted levers 32 and the rollers 30 be lsolated from englne-lnduced shaft vlbratlons.
(a) Field of the Invention This invention relates to a new or improved variable ratio drive pulley or clutch for the transmission of a driving torque to a flexible belt in a belt drive arrangement, the new pulley being particularly although not exclusively useful in a snowmobile drive transmission.
(b) Description of the Prior Art In my U.S. Patent No. 5,326,330, the disclosure of which is hereby incorporated by reference, I describe a drive pulley as utilized in a snowmobile transmission. The drive pulley includes a central axial shaft carrying two frusto-conical flanges one of which is fixed to rotate with the shaft and the other of which is guided to move axially towards and away from the fixed flange. The movable flange is urged away from the fixed flange by a spring, and the pulley includes an arrangement of pivoted weighted levers designed on rotation of the pulley to generate an axial force on the movable flange to displace it towards the fixed flange, this force increasing with rotational speed of the pulley.
A drive pulley of the type discussed above, otherwise described as a clutch, is generally coupled directly to the crankshaft of the engine and thus is subjected to engine induced vibrations at both pulley flanges. In particular, the drive pulley of a snowmobile transmission is commonly mounted directly to the crankshaft of a high specific horsepower two-stroke engine and may be subjected to a very high level of vibration, both bending and torslonal, emanatlng from the englne crankshaft. Thls can be deleterlous both to the force generatlng means and to the drlve belt ltself. Indeed lt ls common for drlve pulleys of thls klnd used ln snowmoblles to experlence wear ln the load mechanlsm or force generatlng means.
Thls wear ls caused malnly by torslonal vlbratlon, and to malntaln optlmum performance of the system lt may be necessary to replace varlous components of the mechanlsm perlodlcally.
The constantly lncreaslng power outputs of snowmoblle englnes applles addltlonal loadlng stresses to the components so that there ls a need to lmprove the reslstance of drlve pulleys to englne lnduced vlbratlons.
SUMMARY OF THE INVENTION
The lnventlon accordlngly provldes a varlable ratlo drlve pulley comprlslng: a) a shaft; b) confrontlng fixed and movable frusto-conlcal flanges mounted on sald shaft to rotate therewlth, sald flxed flange belng flxed to sald shaft and sald movable flange belng gulded to move axlally of sald shaft towards and away from sald flxed flange; c) a sprlng ln sald pulley belng operatlve to urge sald movable flange away from sald flxed flange; d) a centrlfugally responslve mechanlsm ln sald pulley belng operatlve on rotatlon of sald pulley to generate a force urglng sald movable flange towards sald flxed flange, such force lncreaslng wlth the rotatlonal speed of sald pulley; e) a torque transmltter for transmlttlng a drivlng torque from sald shaft to sald movable flange, sald torque transmltter comprlslng an operatlng head assembly flxed to rotate wlth sald shaft, sald head assembly lncludlng a plurallty of radlal drlvlng arms equlangularly spaced about the axls of sald shaft, sald drlvlng arms engaglng abutment surfaces on sald movable flange at a radlal spaclng from sald shaft axis to dellver drlvlng torque to sald movable flange; f) sald head assembly and sald movable flange havlng cooperatlng axlally extendlng gulde surfaces by whlch sald movable flange ls gulded from movement axlally of sald shaft; g) sald head assembly belng connected to sald shaft through a damplng element sald damplng element belng operatlve to attenuate transmlsslon of torslonal vlbratlons from sald shaft to sald movable flange.
The movable flange ls preferably gulded for axlal movement on an axlally extendlng hollow lnput shaft or sleeve, the flxed flange belng attached to the sleeve, and the sleeve carrylng a hub through whlch torque ls transmltted to the centrlfugally responslve means by way of the damplng element. In thls way, the effects of englne-lnduced vlbratlons are absorbed and dampened, and thls protects the centrlfugally responslve means from the damaglng effects of such vlbratlons. Furthermore the effects of vlbratlons transmltted to the drlve belt from the movable flange are substantially ellmlnated.
The element can be posltloned at any convenlent locatlon ln the operatlng head assembly, and ln one preferred arrangement ls located ln the hub reglon thereof.
An added beneflt of the lncorporatlon of the damplng element ls that lt effects a slgnlflcant reductlon ln the level of nolse generated by the varlable ratlo drlve pulley ln operatlon. Thus the lnventlon also provldes a method for reduclng the nolse output of varlable ratlo pulleys of thls general type.
BRIEF DESCRIPTION OF THE DRAWINGS:
The lnventlon wlll further be descrlbed, by way of example only, wlth reference to the accompanylng drawlngs whereln:
Flgure 1 ls a partlally fragmentary cross-sectlonal vlew of a preferred embodlment of varlable ratlo drlve pulley ln accordance wlth the lnventlon;
Flgure 2 ls a sectlonal vlew taken generally on the llne II-II ln Flgure l;
Flgure 3 ls an exploded sectlonal vlew of certaln components shown ln Flgure 2; and Flgure 4 ls a vlew correspondlng to Flgure 2 but showlng a modlfled embodlment of varlable ratlo drlve pulley ln accordance wlth the lnventlon.
DESCRIPTION OF THE PR~h~K~ EMBODIMENT
Referrlng to Flgure 2, the drlve pulley comprlses a hollow tubular shaft 11 whlch carrles opposed frusto-conlcal flanges 12 and 13. The flange 12 ls a flxed flange that ls rlgldly secured to the shaft 11, whereas the flange 13 ls a movable flange gulded for movement axlally of the shaft 11 towards and away from the flxed flange by a bushlng 14. The rear slde of the movable flange 13 carrles ln a hollow houslng 15 closed on lts rear slde by a convex cover 16 that ls detachably secured to the houslng by capscrews 17, the cover havlng a central axlally pro~ectlng hub 18 that carrles a tubular bushlng 19 whlch slldably engages a reduced dlameter portlon 20 of the shaft 11.
The capscrews 17 are slx ln number and are recelved ln threaded engagement ln bores of axlally extendlng bosses 23 (Flgure 2) arranged ln palrs, each boss belng assoclated wlth an ax~ally extendlng gulde wall 24 whlch walls are lntegral wlth the rear slde of the movable flange 13. The gulde walls cooperate wlth the llmbs 25 of a three-armed operatlng head 26 whlch ls mounted to rotate wlth the shaft 11. The operatlng head 26 transmlts drlvlng torque from the shaft 11 to the movable flange whlle permlttlng the latter to move axlally wlth respect to the shaft 11. More speclflcally, near lts extremlty each of the llmbs 25 carrles a palr of pads 27 of low-frlctlon materlal each seated ln a counterbore ln one slde of the llmb, each pad 27 belng ln slldlng engagement wlth one of the gulde walls 24, sprlng means (not shown) belng provlded to take up any clearance between the llmbs 25, pads 27 and gulde walls 24.
Each llmb 25 also carrles a roller 30 rotatably mounted on an axls that ls tangentlal to and ln a plane perpendlcular to the axls of the shaft 11, and ls coaxlal wlth the slldlng pads 27. Each roller 30 ls posltloned between blfurcate flngers 28 belng carrled on a pln 29 mounted ln bores ln the flngers 28 and allgned wlth the pads 27.
Each roller 30 ls mounted to cooperate wlth a cam surface 31 of an ad~ustlng lever 32 whlch extends generally radlally wlth respect to the axls of the shaft 11 and ls plvotally mounted on the rear slde of the movable flange 13 on an axls generally parallel to that of the roller 30. As ls more fully descrlbed ln my U.S. Patent 5,326,330, the plvotal mountlng of each ad~ustlng lever lncludes an ad~ustable 2~ 94522 eccentric 33 by means of whlch the location of the plvotal axis of the lever 32 can be ad~usted. The operation of this ad~ustment in varylng the performance characterlstlcs of the pulley ls as described ln my above ldentlfled prevlous patent, and ls not further descrlbed herein.
As prevlously mentloned, the three-armed operatlng head 26 ls flxed to rotate with the shaft 11. However it is structured so that lt lncludes a vlbratlon absorblng structure thereby to attenuate or ellmlnate vlbratlons transmltted from the shaft to the movable pulley flange 13. Referrlng to Flgure 3, the operatlng head 26 has a large hollow central hub 35 whlch has an lnterlor surface 36 of tapered hexagonal proflle. The proflle reaches a mlnlmum slze at a locatlon 37 near the rlght hand end of the hub as seen ln Flgure 3, and then flares outwardly. Each facet of the lnternal surface 36 has machlned thereln a part-cyllndrical recess 38, the recesses 38 being coaxlal wlth respect to the central axls 40 and each termlnatlng ln a shoulder 41, the shoulders lylng ln a common plane at rlght angles to the axls 40.
A vlbratlon absorbent reslllent damplng member 45 ls slzed to be posltloned wlthln the hub 35 near one end (the rlght hand end as seen ln Figure 3) of the lnterlor surface 36. The damplng member 45 ls of a sultable reslllent materlal such as polypropylene, natural and synthetlc rubbers and the llke, and ls ln the form of an hexagonal rlng slzed to flt closely agalnst the lnternal surface 36. Thus, the outslde of the member 45 has a flrst tapered hexagonal surface 46 and a second shorter expanding hexagonal surface 47, the lnner surface 48 belng contlnuously tapered from one end to the other, and the end surfaces belng ln planes perpendlcular to the axls 40. The slightly enlarged sectlon 47 of the damplng member 45 acts to retaln the latter agalnst dlsplacement rearwardly (to the left as seen ln Flgure 2) and separatlon from the operatlng head 26.
A tubular drlver hub 50 secures the operatlng head 26 wlth respect to the shaft 11, and ls most clearly shown ln Flgure 3. The drlver hub 50 has a screwthreaded bore 51 wlth short cyllndrlcal counterbores at opposlte ends thereof, and has at a medlal posltlon ln lts length a pro~ectlng external annular flange 52. As seen ln Flgure 3, to the rlght of the flange 52 there ls a tapered hexagonal surface sectlon 53 whlch has a proflle that corresponds to that of the lnner surface 48 of the damplng member. Stlll wlth reference to Flgure 3, to the left of the flange 52 the drlver hub has a short cyllndrlcal sectlon 54, and termlnates l~n a short hexagonal drlvlng sectlon 55. The outer dlameter of the flange 52 ls of a slze to flt wlthln the cyllndrlcally formed recesses 38.
In the assembled condltlon, the damplng member 50 ls fltted wlthln the hub 35 and ls posltloned ad~acent a flat annular washer 56 whlch ln turn ls supported agalnst an annular shoulder 57 on the shaft 11 (Flgure 2). The drlver hub 50 ls ln engagement wlth screwthreaded sectlon 58 of the shaft 11, wlth the flange 52 recelved ln the recesses 38 so that the damplng member 45 ls contalned at lts opposlte ends between the flange 52 and the washer 56 and ls contalned at lts lnternal and external perlpherles by the tapered hexagonal drlver surface 53 and the tapered hexagonal hub surface 36 respectlvely. Durlng 2 1 ~4522 assembly, after the flxed flange 12 has been lnstalled on the shaft, the movable flange 13 ls then mounted and the washer 56 placed agalnst the shoulder 57 of the shaft. The damplng member 45 ls then fltted wlthln the bore of the operatlng head 26, and these are then passed over the shaft to the posltlon shown ln Flgure 2 where the damplng member 45 abuts the washer 56. The drlver hub 50 ls then lnstalled, belng threaded onto the screwthreaded sectlon 58 of the shaft to brlng the flange 52 lnto abutment wlth the end surface of the damplng member 45, and compress the latter to the degree deslred.
In the fully lnstalled posltlon the washer 56 ls engaged and clamped agalnst the shoulder 57 by the forward end of the drlver hub 50. Rotatlon of the drlver hub 50 can be effected by a wrench or the llke engaglng the hexagonal drlve sectlon 55 of the hub. In the fully lnstalled posltlon therefore the damplng member 45 ls contalned at lts ends between the washer 56 and the hub flange 52, and on lts lnner and outer sldes between the hexagonal hub surface 53 and the hexagonal surface sectlons 36, 37 of the drlver 26 respectlvely. In thls condltlon there ls no metal-to-metal contact between the operatlng head 26 and the parts (hub 50 and washer 56) attached to the shaft 11. Thus there ls substantlal clearance between the flange 52 and the recesses 38 and shoulders 41 of the operatlng head and between the outer perlphery of the washer 56 and the hub 35 of the operatlng head that no metal-to-metal contact can occur, even lf the hub 50 and the washer 56 undergo substantlal torslonal and bendlng vlbratlon transmltted from the shaft 11.
~ 1 94522 From the foregolng descrlptlon and from a conslderatlon of Flgure 2 of the drawlngs lt wlll be appreclated that the components descrlbed effectlvely flx the operatlng head 26 with respect to the shaft 11 so that torque from the shaft can be transmltted to the operatlng head 26 and thence to the welghted pivoted levers 32 and the movable pulley flange 13.
However as noted above, there ls no contlnuous metal-to-metal engagement ln the path between the shaft 11 and the operatlng head 26. Instead, torque from the shaft ls transmltted through the drlver hub 50 to the damping member 45 and from the latter to the operatlng head 26. Rellable torque transmlsslon ls ensured by the hexagonal shape of the damplng member 45, there belng no need for the latter to be bonded elther to the drlver hub 50 or to the operatlng head 26.
A colled compresslon sprlng 60 ls posltloned wlth one end seated agalnst the cover 16 around the hub 18, and lts opposlte end seated agalnst the flange 52 around the cyllndrlcal sectlon 54 of the drlver hub 50. As lndlcated prevlously, the cover 16 ls flxedly secured to the movable flange 13 by capscrews 17, thls conflguratlon allows the sprlng 60 to apply a compresslve load to and press the lnner sectlon of the movable flange 13 agalnst the washer 56 (adoptlng the posltlon shown ln Flgure 2). When the parts are posltloned as shown ln Flgure 2 wlth the movable flange 13 at lts maxlmum spaclng from the flxed flange 12, the compresslve loadlng applled to the sprlng 60 ls mlnlmal. A low-frlctlon plastlc carrler may be lnterposed between the hub 18 and the ad~acent end of the sprlng 60 to avold frettlng or abraslve wear of hub 18 due to vlbratlon of 2 ~ 94522 the sprlng.
In general, the operatlng characterlstlcs of the drlve pulley are slmllar to those of the drlve pulley descrlbed ln my U.S. Patent 5,326,330. When the shaft 11 ls statlonary or rotatlng at low speed, the components occupy the posltlons shown ln Flgure 2 wlth the movable flange 13 at maxlmum spaclng from the flxed flange 12 so that the flanges do not apply any drlvlng torque to the V-shaped drlvlng belt (not shown) whlch ls located therebetween. Wlth lncreaslng speeds of rotatlon, the centrlfugal force actlng on the ad~ustable levers 32 tends to plvot these outwardly around thelr plvotal mountlngs so that the cam surfaces 31 lnteract wlth the rollers 32 to develop an axlal thrust urglng the movable flange towards the fixed flange. When thls axlal thrust reaches a sufflclent level, lt overcomes the loadlng of the sprlng 60 and the flange 13 is dlsplaced towards the flxed flange 12 to engage the drlve belt therebetween, as ls well understood.
The damplng arrangement descrlbed acts to lsolate the movable flange and all the components assoclated therewlth lncludlng the bushlng 14, the centrlfugal levers 32 and thelr eccentrlcs 33, the cover 16, gulde walls 24 and the operatlng head 26 from the effects of torslonal vlbratlons generated on the englne crankshaft (not shown) to whlch the shaft 11 ls connected. These vlbratlons are partlcularly troublesome ln hlgh output two-stroke englnes of the type commonly used ln recreatlonal vehlcles such as snowmoblles. The damplng assembly lmproves the performance and rellablllty of such products whlle enabllng them to operate more quletly.
2 ~ 94522 Furthermore, testlng has shown that the servlce llfe of a snowmoblle drlve pulley of the type dlsclosed ln my U.S.
Patent 5,326,320 can be greatly lmproved by the addltlon of a damplng arrangement as descrlbed above. In some tests lt was found that the servlce llfe of the drlve pulley was lncreased by a factor of up to 10 before malntenance was requlred.
The use of a damplng arrangement as descrlbed offers a further ma~or beneflt ln that lt provldes a method of achlevlng a slgnlflcant reductlon ln nolse generated durlng operatlon of the drlve pulley. Varlous elements of the mechanlsm lnvolve metal-to-metal or metal-to-plastlc contact and there wlll usually be sufflclent clearance between the components that when the pulley ls sub~ected to vlbratlons, rattllng and hammerlng nolses can be generated. Such nolses are greatly reduced by lncorporatlng a damplng arrangement as descrlbed slnce the latter ls effectlve to more or less completely attenuate vlbratlons whlch otherwlse would be transmltted through the movable components.
Referrlng now to Flgure 4 the overall conflguratlon of the varlable ratlo drlve pulley lllustrated thereln ls slmllar to that as shown ln Flgures 1 to 3 and llke reference numbers are used to ldentlfy llke elements thereof. In contrast to the flrst descrlbed embodlment, ln Flgure 4 there ls no damplng member 45 located ln the reglon of the hub, but rather the three-armed operatlng head 26a has an lntegral hub 35a and lncludes modlfled arms 25a carrylng the damplng elements. More speclflcally, ln each arm there ls a damplng element 45a ln the form of a flat rectangular plece of reslllent damplng materlal bonded to a surface of the arm 25a, these damplng elements 45a lying ln a common plane that ls at rlght angles to the axls of the shaft 11. On lts opposlte slde, each damplng element 45a ls bonded to a co-extenslve flat wall 64 of a carrler 65, thls carrler havlng lntegrally formed thereon the flngers 28 that support the pln 29 and roller 30. As before, the materlal of the damplng elements can be of any sultable natural or synthetlc rubber, for example NBR (Nltrlle-butadlene) of a hardness of 65+5 Shore A.
It wlll be seen that as wlth the flrst descrlbed embodlment, ln the embodlment of Flgure 4 the centrlfugally mechanlsm lnvolvlng the lnter-engaglng rollers 30 and levers 32 as well as the movable flange 13 ltself are effectlvely lsolated from vlbratlons. Thls embodlment also ls effectlve to slgnlflcantly reduce the generatlon of nolse.
Although the lnventlon has been exempllfled ln the foregolng by the descrlptlon of presently preferred embodlments of varlable ratlo drlve pulley, and methods of reduclng the vlbratlon and nolse output thereof, lt wlll be understood that many modlflcatlons can be made ln the detalls of the lnventlon.
Thus, the lnternal and external surfaces of the damplng member 45 ln Flgures 1 to 3 are descrlbed as belng hexagonal, whlle lt wlll be evldent that many other polygonal and non-clrcular shapes would be feaslble. Indeed by bondlng the damplng member 45 (Flgure 2) to the drlver hub 50 andtor to the operatlng head hub 35, lt would be posslble to utlllze cyllndrlcal or conlcal shapes for such bonded surfaces. Slmllarly the damplng member although lllustrated ln Flgures 1 to 3 as belng lncorporated 21 94~22 between the operatlng head and the drlver hub, could ln fact be lncorporated wlthln the operatlng head itself e.g. as shown ln Flgure 4, the determlnlng requlrement belng that the movable flange 13, the welghted levers 32 and the rollers 30 be lsolated from englne-lnduced shaft vlbratlons.
Claims (14)
1. A variable ratio drive pulley comprising:
a) a shaft;
b) confronting fixed and movable frusto-conical flanges mounted on said shaft to rotate therewith, said fixed flange being fixed to said shaft and said movable flange being guided to move axially of said shaft towards and away from said fixed flange;
c) a spring in said pulley being operative to urge said movable flange away from said fixed flange;
d) a centrifugally responsive mechanism in said pulley being operative on rotation of said pulley to generate a force urging said movable flange towards said fixed flange, such force increasing with the rotational speed of said pulley;
e) a torque transmitter for transmitting a driving torque from said shaft to said movable flange, said torque transmitter comprising an operating head assembly fixed to rotate with said shaft, said head assembly including a plurality of radial driving arms equiangularly spaced about the axis of said shaft, said driving arms engaging abutment surfaces on said movable flange at a radial spacing from said shaft axis to deliver driving torque to said movable flange;
f) said head assembly and said movable flange having cooperating axially extending guide surfaces by which said movable flange is guided from movement axially of said shaft;
g) said head assembly being connected to said shaft through a damping element said damping element being operative to attenuate transmission of torsional vibrations from said shaft to said movable flange.
a) a shaft;
b) confronting fixed and movable frusto-conical flanges mounted on said shaft to rotate therewith, said fixed flange being fixed to said shaft and said movable flange being guided to move axially of said shaft towards and away from said fixed flange;
c) a spring in said pulley being operative to urge said movable flange away from said fixed flange;
d) a centrifugally responsive mechanism in said pulley being operative on rotation of said pulley to generate a force urging said movable flange towards said fixed flange, such force increasing with the rotational speed of said pulley;
e) a torque transmitter for transmitting a driving torque from said shaft to said movable flange, said torque transmitter comprising an operating head assembly fixed to rotate with said shaft, said head assembly including a plurality of radial driving arms equiangularly spaced about the axis of said shaft, said driving arms engaging abutment surfaces on said movable flange at a radial spacing from said shaft axis to deliver driving torque to said movable flange;
f) said head assembly and said movable flange having cooperating axially extending guide surfaces by which said movable flange is guided from movement axially of said shaft;
g) said head assembly being connected to said shaft through a damping element said damping element being operative to attenuate transmission of torsional vibrations from said shaft to said movable flange.
2. A variable ratio drive pulley as claimed in claim 1 wherein said shaft carries an annular hub that encloses and is attached to a portion of said shaft, said head assembly including an outer part which incorporates said driving arms and which has an inner periphery that is in register with an outer peripheral portion of said hub, said damping element comprising a ring of resilient damping material that is interposed between said hub and said inner periphery, and that is mounted to accommodate vibrational movements between said hub and said outer part.
3. A variable ratio drive pulley as claimed in claim 2 wherein said ring of resilient damping material has an outer profile and an inner profile which are both of non-circular outline to engage elements of complementary outline associated with said hub and said head assembly respectively whereby to transmit torque between said shaft and said head assembly while absorbing vibrations.
4. A variable ratio drive pulley as claimed in claim 3 wherein said ring of resilient damping material is of polygonal outline in a plane normal to said shaft axis.
5. A variable ratio drive pulley as claimed in claim 3 wherein said ring of resilient damping material is compressed axially between an abutment face associated with said shaft and a radial flange on said hub.
6. A variable ratio drive pulley as claimed in claim 3 wherein said hub is mounted in engagement with said shaft portion, and is rotatable by means of a tool to adjustably compress said ring of resilient damping material.
7. A variable ratio drive pulley as claimed in claim 5 wherein said abutment face is provided on an annular ring that is supported on a shoulder on said shaft, said ring having an opposite side which provides an abutment for engagement by said movable flange in limiting the maximum spacing of said movable flange from said fixed flange.
8. A variable ratio drive pulley as claimed in claim 6 wherein said spring comprises a coiled compression spring one end of which seats on said hub and an opposite end of which seats on a cup which is attached to move with said movable flange and which supports the axially extending guide surfaces thereof.
9. A variable ratio drive pulley as claimed in claim 2 wherein said damping element is bonded to at least one of said hub and said inner periphery of said head assembly.
10. A variable ratio drive pulley comprising:
a) a shaft;
b) confronting fixed and movable frusto-conical flanges mounted on said shaft to rotate therewith, said fixed flange being fixed to said shaft and said movable flange being guided to move axially of said shaft towards and away from said fixed flange;
c) a spring in said pulley being operative to urge said movable flange away from said fixed flange;
d) a torque transmitter for transmitting a driving torque from said shaft to said movable flange, said torque transmitter comprising an operating head assembly fixed to rotate with said shaft, said head assembly including a plurality of radial driving arms equiangularly spaced about the axis of said shaft, said driving arms engaging abutment surfaces on said movable flange at a radial spacing from said shaft axis to deliver driving torque to said movable flange;
e) said head assembly and said movable flange having cooperating axially extending guide surfaces by which said movable flange is guided from movement axially of said shaft;
f) a centrifugally responsive mechanism acting between said movable flange and said operating head assembly in said pulley and being operative on rotation of said pulley to generate a force urging said movable flange against the urging of said spring towards said fixed flange, such force increasing with the rotational speed of said pulley;
g) said head assembly being connected to said centrifugally responsive mechanism through a damping element said damping element being operative to attenuate transmission of torsional vibrations from said shaft to said movable flange.
a) a shaft;
b) confronting fixed and movable frusto-conical flanges mounted on said shaft to rotate therewith, said fixed flange being fixed to said shaft and said movable flange being guided to move axially of said shaft towards and away from said fixed flange;
c) a spring in said pulley being operative to urge said movable flange away from said fixed flange;
d) a torque transmitter for transmitting a driving torque from said shaft to said movable flange, said torque transmitter comprising an operating head assembly fixed to rotate with said shaft, said head assembly including a plurality of radial driving arms equiangularly spaced about the axis of said shaft, said driving arms engaging abutment surfaces on said movable flange at a radial spacing from said shaft axis to deliver driving torque to said movable flange;
e) said head assembly and said movable flange having cooperating axially extending guide surfaces by which said movable flange is guided from movement axially of said shaft;
f) a centrifugally responsive mechanism acting between said movable flange and said operating head assembly in said pulley and being operative on rotation of said pulley to generate a force urging said movable flange against the urging of said spring towards said fixed flange, such force increasing with the rotational speed of said pulley;
g) said head assembly being connected to said centrifugally responsive mechanism through a damping element said damping element being operative to attenuate transmission of torsional vibrations from said shaft to said movable flange.
11. A variable ratio drive pulley as claimed in claim 10 wherein said damping element comprises a respective piece of damping material operatively connected between each said radial driving arm and said centrifugally responsive mechanism.
12. A variable ratio drive pulley as claimed in claim 11 wherein each said piece is bonded to a surface of the respective radial driving arm and a confronting surface associated with said centrifugally responsive means.
13. A variable ratio drive pulley as claimed in claim 12 wherein said centrifugally responsive mechanism comprises a respective pivoted weighted lever in register with each of said radial driving arms each said lever cooperating with a respective roller, said confronting surface being on an element which supports one of said lever and said roller.
14. A variable ratio drive pulley as claimed in claim 13 wherein each said pivoted weighted lever is pivotally mounted on said movable flange through an adjustable mounting.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US08/740,607 | 1996-10-31 | ||
US08/740,607 US5692983A (en) | 1996-10-31 | 1996-10-31 | Variable ratio drive pulley |
Publications (1)
Publication Number | Publication Date |
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CA2194522A1 true CA2194522A1 (en) | 1998-04-30 |
Family
ID=24977284
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002194522A Abandoned CA2194522A1 (en) | 1996-10-31 | 1997-01-07 | Variable ratio drive pulley |
Country Status (2)
Country | Link |
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US (1) | US5692983A (en) |
CA (1) | CA2194522A1 (en) |
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US10393263B2 (en) * | 2016-09-16 | 2019-08-27 | Don Simpson | Rebuild kit for a CVT clutch spider |
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CA3033684A1 (en) * | 2018-11-28 | 2020-05-28 | Xavier-Pierre Aitcin | Drive pulley for a continuously variable transmission |
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1997
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Also Published As
Publication number | Publication date |
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US5692983A (en) | 1997-12-02 |
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